zo 



ZOOLOGY 



include a 

 The most 

 They may 



Europe, limpots fPatella, Fig. 209j are used as food ; but on our 

 Eastern coast they are too rare for this. 



The hinder-gilled mollusks (Opisthobranchs) 

 large proportion of sj'mmetrieal shell-less species, 

 familiar of these are the sea-slugs, 

 be found among hydroids hanging from rocks, 

 or in tide-pools. Our species are usually less 

 than twenty millimetres long. They are often 

 covered with numerous gills, which give them a 

 velvety aspect. When placed in an aquarium, 

 they laj' eggs in gelatinous coils on the hydroid 

 stems. Eolis ^ is a common genus (Fig. 210). 

 Besides the gasteropods, two groups of mol- 

 lusks majr be briefly mentioned here. In one 

 Fig. 210. — Eolis. group the body is very symmetrical, not only 

 externally, but also internally, which is not true of most 

 symmetrical gasteropods. A common representative is Chiton'^ 

 (Fig. 211). This animal has a sort of coat of mail, since its 

 shell is made up of eight pieces, lying one 

 behind the other, along its back. When re- 

 mo^'ed from the rock or shell on which it rests, 

 it coils up like a pill-bug or armadillo. 



Coordinate with the Gasteropoda is the 

 group of squids and cuttlefishes (Ceph'alo- 

 poda'). They have a large, distinct head, 

 a circle of arms about the mouth, a funnel- 

 shaped foot, and huge eyes on each side of the head (Fig. 212). 

 The squids are the best-known cephalopods, since they travel 



' Eolis, daughter of Eolus, the Rod of the winds. 

 2 Coat, case, covering. 



^ kephale, head ; pou.'i, foot ; becau,se the arms or foot are placed around 

 the mouth. 



Fig. 2U.^ Chiloti 

 (Trachydcmion) 

 apiculatus, the 

 armadillo snail. 

 Nat. size. Photo, 

 bv W. H. C. P. 



